The invention relates to a spring mechanism typically used for biasing hoods, tops, doors, hinged covers, and other elements from a closed to an open position. The invention involves the use of springs in conjunction with a rod member to exert a driving force on the elements to be displaced. The following patents are incorporated herein by reference as background information with regard to spring mechanisms: U.S. Pat. No. 6,199,843 to DeGrace; U.S. Pat. No. 5,810,339 to Küspert, et al.; and U.S. Pat. No. 4,962,916 to Palinkas.
Compression spring rods are used in various applications; for example, to assist in lifting, opening, and damping. Typical applications include lifting a lid hinged to a stationary base. Other applications include lifting and/or balancing elements for a trunk or hood of an automobile. The present invention uses the compression spring rod assembly to assist a hood of a bus during opening of the hood and securing the hood in place in a fully opened position. A two stage spring assembly is used in which the first stage spring assists during the opening process and the second stage spring assembly is used to prevent the hood from falling after passing a center of gravity point of the hood.
Existing mechanical lifts for bus hoods, such as for school busses, use a combination of extension springs and cable for assisting opening and closing of the bus hoods. The force needed to open a school bus hood is typically required to be less than 25 lbs. The existing systems have difficulty meeting this requirement. In contrast, the two stage spring assembly of the present invention only requires approximately 15 lbs. of handle load to open the hood. The system assists the hood in opening, and slows the hood as it approaches the end of the stroke and limits the travel of the hood. Accordingly, it is considered desirable to provide a new and improved two stage spring assembly which overcomes the foregoing difficulties and others while providing better and more advantageous results.
Typically, bus hoods are oriented such that the top of the hood is essentially parallel to the ground thus providing the driver with a limited line of vision with respect to objects or persons in front of the bus. An improved bus hood design provides a downward angle or slope to the top of the hood from the windshield thus providing increased visibility to the area in front of the bus. Thus, the driver has a better view of either objects or children or persons walking in front of or positioned in front of the bus. Thus, the slant or slope design of the hood increases the safety to people around the bus while the bus is either stationary or in transit.
The hood is lifted away from the windshield towards the front of the bus. Once the hood passes a vertical position balanced with respect to its center of gravity, it tends to drop or fall due to gravity and may injure the person opening the hood. Thus, a two stage spring assembly is desired for controlling movement of the hood before and after it reaches a vertical position balanced at its center of gravity.